Frank Capley (left) and Joe Alfano protest the San Francisco county clerk's denial of marriage licenses to same-sex couples on Feb. 14.

Justin Sullivan
/ Getty Images

Originally published on March 20, 2013 4:09 pm

Sen. Rob Portman, an Ohio conservative Republican who recently said he now supports same-sex marriage because he has a gay son, evidently has plenty of company.

A new poll from the Pew Research Center for the People and the Press suggests that many Americans have changed their minds — going from opposing to supporting same-sex marriage — because they personally know someone who is gay.

Overall, 28 percent of gay-marriage supporters say they used to be opponents. The reason most often given was that someone in their personal circle — a family member, friend or acquaintance — is gay.

The survey indicates that 16 percent of all Americans say they have changed their mind one way or the other on the issue; most overwhelmingly (14 percent of the 16 percent) switched from opposing to supporting gay marriage.

In the poll conducted between March 13 and March 17, 49 percent of those surveyed said they support gay marriage, while 44 percent said they are opposed. The margin of error was just shy of 4.5 percentage points.

Ten years ago, 56 percent of those surveyed said they opposed same-sex marriage, and 34 percent supported it.

The findings come just a week before the U.S. Supreme Court hears a pair of cases on the issue.

As many other polls have found, the shift in American attitudes on same-sex marriage seems largely a generational affair, with younger people being much more supportive than the generations of their parents and grandparents.

Of those in the so-called millennial generation — those born after 1980 and who are 18 and older but younger than 32 — 70 percent support same-sex marriage.

But there's been a significant shift to higher support among older Americans, too. Support for same-sex marriage has risen to 31 percent among people born between 1928 and 1945, the poll found, compared with just 17 percent 10 years ago.